Scientists Crack SARS Genetic Sequence

Bronchial tissue from a victim of SARS in Toronto yielded the virus sample that Canadian scientists sequenced. In a process known as "reverse transcription," the team made a DNA copy to be used in a biochemical reaction.

About 30 scientists at the Genome Sciences Centre set aside their regular cancer research to work on the sequencing. Aided by advanced molecular technology and some good luck with the volatile chemical reactions, they unraveled the genetic code in just a week, a remarkably fast achievement.

"It took three years to find the cause of AIDS and HIV," said Dick Thompson, spokesperson for the World Health Organization. "It took eight days to find the cause of this disease."

Scientists at the Centers for Disease Control in Atlanta, meanwhile, used a sample from a SARS victim in Hanoi, Vietnam, to complete their genetic sequencing. The two studies produced identical results.

The lab work has taken on crucial significance after WHO officials, in China to investigate the origins of the SARS outbreak, this weekend said they suspected field work may never reveal the source of the disease.

The outbreak began in November, but Chinese authorities didn't acknowledge it until several months later. Health experts have strongly criticized the Chinese government for trying to keep the epidemic a secret.

Testing Suspected Carriers

The scientists have posted the viral sequence on the Internet for researchers around the world to investigate further. They hope the genetic blueprint will lead to the development of new diagnostic tests for the disease. Such tests, which may require only a saliva sample, could determine if a potential patient has SARS and help in segregating those affected by the virus.

The sequencing may also help explain how the virus mutated into something so deadly. "The next step for the Genome Sciences Centre is to analyze the proteins that the virus produces, to find clues for why this is such a virulent pathogen," said Steven Jones of the Genome Sciences Centre.

Ultimately, the new information could lead to the discovery of a new vaccine against SARS, but this may take many years. Because the coronaviruses mutate so rapidly, it's very difficult to devise a vaccine for them. There is, for example, no vaccine for the cold. "We still have a long way to go," said Lai. "We don't have the upper hand yet, but we gained an important armament in the fight against SARS."